Among the pathogens thought to represent the greatest threat as bioweapons are Bacillus anthracis, Francisella tularensis and smallpox, which are all CDC designated category A pathogens. As bioweapons they are particularly troublesome because they use the pulmonary route and produce diseases that are unusually difficult to diagnose and treat. Further, we know very little about the interaction of these pathogens with the lung environment. The two primary protective options available are: 1) development of vaccines that induce effective acquired immunity against lung infections and/or 2) development of therapeutics that enhance innate immunity. Understanding the mechanisms by which innate and acquired immunity protect against pulmonary challenge with category A pathogens is critical for developing new therapeutics. None of these pulmonary biothreat infections have a high enough incidence in nature to allow us to determine efficacy using standard epidemiological and statistical analysis. Therefore, we must rely heavily on well characterized animal models. We have developed murine pulmonary models for anthrax, virulent tularemia and cowpox virus. We have partnered with Lovelace Respiratory Research Institute to address the interactions of these pathogens with the lung. The Project Leaders of the projects and Cores bring complementary expertise to this Program Project that will provide significant synergy for all of the projects and their aims. Project 1 (Lipscomb) will use defined B. anthracis mutants to investigate the role of the primary virulence factors in dissemination from the lung and induction of end organ damage in murine and nonhuman primate models of inhalation anthrax. It will also investigate the role of alveolar macrophages and complement in preventing dissemination. Project 2 (Pickup) will address the host factors responsible for protection from a pulmonary orthopox virus infection and define the role of poxvirus accessory proteins in pulmonary infections. Project 3 (Lyons) will use a recently developed murine model of LVS vaccination induced protection against a pulmonary infection with Biovar A F. tularensis to define the immune mechanisms responsible for protection. Protective mechanisms identified in the murine model will be compared with those identified in an aerosol exposed nonhuman primate model. In partnership with Macrogenics, we will use Expression Library Immunization to interrogate the F. tularensis genome for vaccine candidates.